Liquid-sealed vibration control equipment and elastic partition film for use therein

ABSTRACT

A hydraulic antivibration device capable of sufficiently reducing strange sounds is provided. The one in a first embodiment includes first ribs whose tops are spaced apart from lattice members and second ribs having tops abutting on the lattice members and a smaller rib width than the first ribs. When an elastic partition membrane impinges on the lattice members with vibration, the second ribs resist and the elastic partition membrane impinges moderately on the lattice members, so that strange sounds can be reduced. In a second embodiment, such first and second displacement-regulating protrusions are provided that are disposed asymmetrically relative to a phantom plane passing through a center of the elastic partition membrane in its thickness direction. When the elastic partition membrane is displaced, the displacement-regulating protrusions on the opposite side to the displacement direction intensify the stiffness of it locally, so that the elastic partition membrane is difficult to displace, leading to an effective reduction of strange sounds.

TECHNICAL FIELD

This invention relates to a hydraulic style antivibration device whichis made up of a first attachment fitting, a cylindrical secondattachment fitting, a vibration-isolating base connecting the secondattachment fitting and the first attachment fitting together andcomposed of a rubber-like elastomer, a diaphragm attached to the secondattachment fitting to form a liquid-filled chamber between it and thevibration-isolating base, a partition comparting the liquid-filledchamber into a first liquid chamber on the vibration-isolating base sideand a second liquid chamber on the diaphragm side, and an orificebringing the first and second liquid chambers into communication witheach other, the partition including an elastic partition membrane and apair of lattice members regulating the displacement amount of theelastic partition membrane from both sides thereof, and to the elasticpartition membrane used for the aforesaid hydraulic antivibrationdevice.

BACKGROUND ART

The aforementioned hydraulic antivibration device is installed, forexample, on automobiles between the engine and the vehicle body framethereof. And when a large amplitude vibration attributable toirregularity of a traveling road surface is generated, the liquid flowsthrough the orifice to fluidize between both liquid chambers therebydamping the vibration by reason of the fluidization effect of the fluid.On the other hand, when a fine amplitude vibration is generated, theelastic partition membrane is subjected to reciprocating deformation todampen the vibration, without the liquid flowing through between bothliquid chambers.

In this type of hydraulic antivibration device, strange (unusual) soundsare liable to be generated when the elastic partition membrane impingeson the lattice members. To cope with that, hitherto the lattice membershave been provided with radial ribs, as disclosed in FIG. 4 of JP PatentPublication-A-6-221368. The elastic partition membrane was constructedso that it can be situated in a spaced relation to the lattice members.

However, according to the conventional construction described above,strange sounds could be reduced to some degree, but collision soundsupon impingement of the elastic partition membrane on the ribs of thelattice members was inevitable, and hence, a problem existed in that itwas not possible to reduce sufficiently strange sounds.

This invention has been made to solve the above-mentioned problem, andit is an object of the invention to provide a hydraulic antivibrationdevice capable of reducing sufficiently strange sounds and an elasticpartition membrane used for the hydraulic antivibration device.

DISCLOSURE OF THE INVENTION

In order to attain this object, the hydraulic antivibration device of afirst invention comprises a first attachment fitting, a secondattachment fitting in a cylindrical form, a vibration-isolating baseconnecting the second attachment fitting and the first attachmentfitting to each other and made of a rubber-like elastomer, a diaphragmattached to the second attachment fitting to form a liquid-filledchamber between the diaphragm and the vibration-isolating base, apartition comparting the liquid-filled chamber into a first liquidchamber on the vibration-isolating base side and a second liquid chamberon the diaphragm side, and an orifice putting the first and secondliquid chambers into communication with each other, the partitionincluding an elastic partition membrane and a pair of lattice membersregulating the displacement amount of the elastic partition membranefrom both sides thereof. And the device is constructed so that theelastic partition membrane is provided on both faces thereof with ribgroups projectingly, and the rib groups include a plurality of firstribs and a plurality of second ribs existing in a mutually intermingledfashion, wherein the first ribs are set in such a height dimension thattops of them are situated to be spaced apart from the lattice membersand the second ribs are set in such a height dimension that tops of themabut on the lattice members and in a rib width smaller than the firstribs.

The hydraulic antivibration device of a second invention is directed tothe hydraulic antivibration device of the first invention, wherein theaforesaid first ribs are disposed on the faces of the elastic partitionmembrane so as to be capable of surrounding lattice holes every apredetermined number of them and the aforesaid second ribs are disposedon the faces of the elastic partition membrane in a distributed manner.

The hydraulic antivibration device of a third invention is directed tothe hydraulic antivibration device of the second invention, wherein thelattice holes are arranged in a plurality of rows in the circumferentialdirection of the lattice members, and the aforesaid first ribs areconfigured in an annular fashion so as to be capable of abutting on suchportions of the lattice members that are located on radially both sidesof each row of the lattice holes thereof whereas the aforesaid secondribs are arranged in a radial fashion relative to an axis center of theelastic partition membrane.

The hydraulic antivibration device of a fourth invention is directed tothe hydraulic antivibration device of the first invention, wherein theaforesaid first and second ribs are arranged on the faces of the elasticpartition membrane so that they can surround lattice holes every apredetermined number of them.

The hydraulic antivibration device of a fifth invention comprises afirst attachment fitting, a second attachment fitting in a cylindricalform, a vibration-isolating base connecting the second attachmentfitting and the first attachment fitting to each other and composed of arubber-like elastomer, a diaphragm attached to the second attachmentfitting to form a liquid-filled chamber between the diaphragm and thevibration-isolating base, a partition comparting the liquid-filledchamber into a first liquid chamber on the vibration-isolating base sideand a second liquid chamber on the diaphragm side, and an orificeputting the first and second liquid chambers into communication witheach other, the partition including an elastic partition membrane, acylinder portion accommodating the elastic partition membrane, and apair of lattice members regulating the displacement amount of theelastic partition membrane from both sides thereof, wherein the onelattice member of the aforesaid pair of lattice members is joinedintegrally with the cylinder portion between inner peripheral facesthereof, and the elastic partition membrane is provided on both facesthereof with a plurality of ribs capable of surrounding lattice holesevery a predetermined number of them.

The hydraulic antivibration device of a sixth invention is directed tothe hydraulic antivibration device of the fifth invention, wherein theelastic partition membrane is provided on both faces thereof with aplurality of auxiliary ribs arranged in a distributed manner, theaforesaid ribs are set in such a height dimension that tops of them aresituated to be spaced apart from the lattice members, and the aforesaidauxiliary ribs are set in such a height dimension that tops of them abuton the lattice members and in rib width smaller than the ribs.

The hydraulic antivibration device of a seventh invention is directed tothe hydraulic antivibration device of the sixth invention, wherein theaforesaid lattice holes are disposed in a plurality of rows in thecircumferential direction of the lattice members, and the aforesaidplural ribs are configured in an annular fashion such that the ribs canabut on such portions of the lattice members that are situated onradially both sides of each row of the lattice holes and the aforesaidauxiliary ribs are arranged in a radial fashion relative to an axiscenter of the elastic partition membrane.

The hydraulic antivibration device of an eighth invention comprises afirst attachment fitting, a second attachment fitting in a cylindricalform, a vibration-isolating base connecting the second attachmentfitting and the first attachment fitting to each other and composed of arubber-like elastomer, a diaphragm attached to the second attachmentfitting to form a liquid-filled chamber between the diaphragm and thevibration-isolating base, a partition comparting the liquid-filledchamber into a first liquid chamber on the vibration-isolating base sideand a second liquid chamber on the diaphragm side, and an orificeputting the first and second liquid chambers into communication witheach other, the partition including an elastic partition membrane and apair of lattice members regulating the displacement amount of theelastic partition membrane from both sides thereof, wherein the elasticpartition membrane is provided on its one face side with firstdisplacement-regulating protrusions and on its other face side or anopposing face of the lattice member thereto with seconddisplacement-regulating protrusions projectingly, and the firstdisplacement-regulating protrusions are arranged in an asymmetricposition to the second displacement-regulating protrusions relative to aphantom (hypothetical) plane passing through a center of the elasticpartition membrane in its thickness direction.

The hydraulic antivibration device of a ninth invention is directed tothe hydraulic antivibration device of the eighth invention, wherein thesecond displacement-regulating protrusions are provided projectingly onthe other face of the elastic partition membrane.

The hydraulic antivibration device of a tenth invention is directed tothe hydraulic antivibration device of the eighth or the ninth invention,wherein at least part of the second displacement-regulating protrusionsare disposed in plural number in a radial fashion relative to an axiscenter of the elastic partition membrane, and at least part of the firstdisplacement-regulating protrusions are disposed in a radial fashionrelative to an axis center of the elastic partition membrane in a nearlyintermediate position between a pair of the seconddisplacement-regulating protrusions disposed radially and adjacently.

The hydraulic antivibration device of an eleventh invention is directedto the hydraulic antivibration device of the ninth invention, whereinthe first displacement-regulating protrusions and the seconddisplacement protrusions, respectively in pieces of n, are disposed in aradial fashion relative to an axis center of the elastic partitionmembrane and substantially equidistantly in the circumferentialdirection so that the first displacement-regulating protrusions may bedeviated in the circumferential direction to the seconddisplacement-regulating protrusions by a rotation angle of about π/n,and the first displacement-regulating protrusions and the seconddisplacement protrusions are configured in substantially the sameprotrusion height and substantially the same protrusion width.

In the eleventh invention, by the passage ‘disposed in a radial fashion“relative to an axis center” of the elastic partition membrane’ is meantthat the respective displacement-regulating protrusions are disposed ina radial fashion “from the axis center toward outwardly”, and the letter“n” stands for an integer of 1 or upwards. The symbol “π” stands for theratio of circumference to diameter of a circle (ca. 3.14) and the unitof the “rotation angle of π/n” is rad (radian).

For example, an elastic partition membrane 115 (cf. FIG. 16) in thesecond embodiment, which will be described below, has first and seconddisplacement-regulating protrusions 151 a, 151 b respectively of fourpieces (n=4) disposed nearly equidistantly (90 degree intervals) in thecircumferential direction, wherein the first displacement-regulatingprotrusions 151 a are deviated circumferentially to the seconddisplacement-regulating protrusions 151 b by a rotation angle of 45degrees (=π/4 rad).

The hydraulic antivibration device of a twelfth invention is directed tothe hydraulic antivibration device of any one of the eighth to theeleventh inventions, wherein the first displacement-regulatingprotrusions and the second displacement-regulating protrusions areconfigured in such a height that tops of them can abut on the latticemembers or the elastic partition membrane.

The hydraulic antivibration device of a thirteenth invention is directedto the hydraulic antivibration device of any one of the eighth to thetwelfth inventions, wherein the elastic partition membrane is furtherprovided with auxiliary protrusions having a lower protrusion height anda narrower protrusion width than the first displacement-regulatingprotrusions.

The elastic partition membrane of a fourteenth invention is used for thehydraulic antivibration device of any one of the first to the thirteenthinventions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a hydraulic antivibrationdevice in a first embodiment of the invention.

FIG. 2 is a plan view of a cylinder member.

FIG. 3 is a front elevational view in longitudinal cross-section of thecylinder member.

FIG. 4 is a side elevational view of the cylinder member.

FIG. 5 is a plan view of a partition membrane displacement-regulatingmember (a partition membrane's displacement-regulating member).

FIG. 6 is a front elevational view of the partition membranedisplacement-regulating member.

FIG. 7 is a plan view of an elastic partition membrane.

FIG. 8 is a cross-sectional view taken along A-A line in FIG. 7.

FIG. 9 is a sectional view taken along B-B line in FIG. 7.

FIG. 10 is a plan view of a partition.

FIG. 11 is a sectional view taken on C-O-C line in FIG. 10.

FIG. 12 is a longitudinal sectional view of a hydraulic antivibrationdevice in a second embodiment of the invention.

FIG. 13 (a) is a plan view of a cylinder member and FIG. 13 (b) is aside elevation of the cylinder member.

FIG. 14 is a sectional view taken on D-D line in FIG. 13.

FIG. 15 (a) is a plan view of a partition membranedisplacement-regulating member and FIG. 15 (b) is a sectional view takenon E-E line in FIG. 15 (a).

FIG. 16 (a) is a top plan view of an elastic partition membrane, FIG. 16(b) is a side elevation of the elastic partition membrane, and FIG. 16(c) is a bottom plan view of the elastic partition membrane.

FIG. 17 is a sectional view taken on F-F line in FIG. 16 (a).

FIG. 18 is an illustrative representation of Comparative Examples 1 to 3showing respective top planes and bottom planes of them.

FIG. 19 is an illustrative representation of Examples 1 to 3 showingrespective top planes and bottom planes of them.

FIG. 20 is a graphical representation showing results of a strange soundevaluation test.

FIG. 21 (a) is a plan view of Comparative Example 1, and FIG. 21 (b) isa plan view of Example 1.

FIG. 22 (a) through FIG. 22 (c) are diagrammatic developments taken onG-G line in FIG. 21 (a) and show deformation states of the elasticpartition membrane.

FIG. 23 (a) through FIG. 23 (c) are diagrammatic developments taken onH-H line in FIG. 21 (b) and show deformation states of the elasticpartition membrane.

DESCRIPTION OF REFERENCE CHARACTERS

-   100, 200 hydraulic antivibration device-   1, 101 first attachment fitting (or first attachment fixture)-   2, 102 second attachment fitting (or second attachment fixture)-   3, 103 vibration-isolating base-   8 liquid-filled chamber-   9 diaphragm-   11A first liquid chamber-   11B second liquid chamber-   12, 112 partition-   16, 116 cylinder member (cylinder portion)-   25, 125 orifice-   15, 115 elastic partition membrane-   17, 117 partition membrane displacement-regulating member (lattice    member)-   18, 118 lattice wall (lattice member)-   50 rib group-   51 first rib (rib)-   52 second rib (auxiliary rib)-   151 a first displacement-regulating protrusion-   151 b second displacement-regulating protrusion-   152 a first auxiliary protrusion (auxiliary protrusion)-   152 b second auxiliary protrusion (auxiliary protrusion)-   54, 154 lattice hole-   54A˜54C, 154A˜154C lattice hole-   P,T axis center of elastic partition membrane

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the invention will be hereinafter describedwith reference to the accompanying drawings. In FIG. 1 the hydraulicantivibration device 100 in a first embodiment is illustrated.

The hydraulic antivibration device 100 is, as shown in FIG. 1, made upof the first attachment fitting 1 to be attached to an engine ofautomobiles, the second attachment fitting 2 in a cylindrical form to beattached to a vehicle body frame beneath the engine, and thevibration-isolating base 3 connecting these and composed of arubber-like elastomer.

As illustrated in FIG. 1, the first attachment fitting 1 is fashioned ina plate form and provided at its central part with an upwardlyorientated attachment bolt 6 in a projecting manner. The secondattachment fitting 2 includes a cylindrical fitting 4, to which thevibration-isolating base 3 is vulcanization molded, and a cup-shapedbottom fitting 5 which is provided at its central part with a downwardlyorientated attachment bolt 6 in a projecting manner.

The vibration-isolating base 3 is formed in a conical frustum shape. Asshown in FIG. 1, the upper end face thereof is vulcanization bonded tothe first attachment fitting 1, and the lower end part thereof isvulcanization bonded to an upwardly splaying upper end opening of thecylindrical fitting 4. At the underside of the vibration-isolating base3, there is defined an upwardly narrowing hollow part, and at the lowerend of the vibration-isolating base 3, a rubber membrane 7 covering theinner peripheral face of the cylindrical fitting 4 joins.

At the second attachment fitting 2, the diaphragm 9 fashioned in apartially spherical form from a rubber membrane is attached as shown inFIG. 1, and between the diaphragm 9 and the underside of thevibration-isolating base 3, the liquid-filled chamber 8 is formed. Theliquid-filled chamber 8 is sealed with liquid. The diaphragm 9 iscovered with the bottom fitting 5.

As illustrated in FIG. 1, the liquid-filled chamber 8 is comparted bythe partition 12 (cf. FIGS. 10 and 11) into the first liquid chamber 11Aon the vibration-isolating base 3 side and the second liquid chamber 11Bon the diaphragm 9 side. The partition 12 is pinched and held in placeby a pinching member 14 provided on the inner periphery side of thesecond attachment fitting 2 and the vibration-isolating base 3.

The partition 12 is made up of the elastic partition membrane 15configured in a disc shape from a rubber membrane, the cylinder member16 accommodating the elastic partition membrane 15 to receive it withthe lattice wall 18 on the inner periphery side thereof, and thepartition membrane displacement-regulating member 17 in a lattice discshape covering the opening of the cylinder member 16 at its one end(upper side in FIG. 1). That is, the lattice wall 18 and the partitionmembrane displacement-regulating member 17 serve to regulate thedisplacement amount of the elastic partition membrane 15 from both sidesthereof.

Between the outer peripheral face of the cylinder member 16 and theinner peripheral face of the second attachment fitting 2, the orifice 25is formed. Here, referring to FIGS. 2 to 4, a description is made of theorifice 25. The orifice 25 is an orifice passage for putting the firstliquid chamber 11A and the second liquid chamber 11B into communicationwith each other (cf. FIG. 1) and makes two rounds about an axis center Oof the cylinder member 16 as shown in FIGS. 2 to 4.

Stated another way, the orifice 25 consists of an orifice passage R1constituting an upper one round and an orifice passage R2 constituting alower one round. The upper and lower orifice passages R1, R2 arepartitioned by an orifice-forming wall 22. The upper orifice passage R1communicates through an opening 19 (cf. FIG. 5) of the partitionmembrane displacement-regulating member 17 and a cutout 55 with thefirst liquid chamber 11A. The lower orifice passage R2 communicatesthrough an opening 58 (cf. FIG. 1) of the pinching member 14 with thesecond liquid chamber 11B.

Returning to FIG. 1, the pinching member 14 is made up of a flat plateportion 28 on its outer periphery side, a first cylinder portion 29infixing in the lower end of the rubber membrane 7, a flat plate portion30 on its intermediate portion side forcing on the other end of thecylinder member 16, and a second cylinder portion 31 infixing in anopening of the cylinder member 16 on its other end side (lower side inFIG. 1). The flat plate portion 28 on the outer periphery side is fixedby crimping together with an attachment plate 10 of the diaphragm 9 andthe bottom fitting 5 by turning up the lower end of the cylindricalfitting 4.

The partition membrane displacement-regulating member 17 will bedescribed with reference to FIGS. 5 and 6. The partition membranedisplacement-regulating member 17 as shown in FIGS. 5 and 6 is providedon its outer periphery side with a cylinder portion 20, which is in turnexternally fitted on one end of the cylinder member 16 (cf. FIG. 1). Andan upper end of the partition membrane displacement-regulating member 17is received on a step 57 of the vibration-isolating base 3 in the axiscenter direction of the cylinder member 16 (cf. FIG. 1).

The lattice holes 54 of the partition membrane displacement-regulatingmember 17 are comprised of, as shown in FIGS. 5 and 6, the lattice hole54C on the central side, and the lattice holes 54A, 54B arranged in tworows in the circumferential direction of the partition membranedisplacement-regulating member 17.

The number of the lattice holes 54A in the inner row is four while thenumber of the lattice holes 54B in the outer row is eight. As shown inFIG. 5, they are arranged at intervals of respective equal angles (90degrees or 45 degrees). And besides, the inner row of the lattice holes54A are adapted in circumferential position to the outer row of thelattice holes 54B located every 45 degrees.

The configuration of the lattice hole rows is as depicted in FIG. 5 suchthat circumferentially extending annular holes are divided in a radialway. As mentioned above, the opening 19 is an aperture bringing thefirst liquid chamber 11A and the orifice 25 into communication with eachother.

The lattice holes 54 of the lattice wall 18 also comprise the centrallattice hole 54C, and the lattice holes 54A, 54B arranged in two rows inthe circumferential direction of the lattice wall 18 (cf. FIGS. 2 to 4).The pattern (number, shape, position about the axis center O of thelattice wall 18, etc.) of them is identical to that on the partitionmembrane displacement-regulating member 17 side.

However, the cylinder portion 20 of the partition membranedisplacement-regulating member 17 is externally fitted on the cylindermember 16 so that the lattice holes 54A, 54B of the lattice wall 18 maybe deviated in position in the circumferential direction from thelattice holes 54A, 54B of the partition membrane displacement-regulatingmember 17 (cf. FIG. 10). The positions of both the central lattice holes54C are the same.

Now the elastic partition membrane 15 will be described with referenceto FIGS. 7 to 9. The partition membrane 15 is, as shown in FIGS. 7 to 9,provided on its both faces with the rib groups 50 in a projectingmanner. The pattern of the rib group 50 on the one face and the patternof the rib group 50 on the other face are the same.

The rib groups 50 each consist of a plurality of the first ribs 51 and aplurality of the second ribs 52.

As shown in FIG. 7, a plurality of the first ribs 51 are configured inan annular fashion relative to the axis center P of the elasticpartition membrane 15 and set in height dimension so that tops of themmay be spaced apart from the lattice wall 18 (or the partition membranedisplacement-regulating member 17) (cf. FIG. 11). That is, in astationary state where no hydraulic pressure acts, a clearance of apredetermined dimension is formed between the tops of the first ribs 51and the lattice wall 18 (or the partition membranedisplacement-regulating member 17).

By the passage recited in claim 1 or claim 6 that “the tops of the firstribs are situated to be spaced apart from the lattice member” is meantthat the height dimension of the first ribs is set to have the aforesaidclearance in the aforesaid stationary state. Therefore, it is notrequired also when a hydraulic pressure acts to displace the elasticpartition membrane that “the tops of the first ribs are situated to bespaced apart from the lattice member”.

A plurality of the first ribs 51 are constructed to be capable ofabutting on lattice member portions 53 (cf. FIGS. 2 and 5) on radiallyboth sides of the respective lattice hole rows of the lattice wall 18(or the partition membrane displacement-regulating member 17) when ahydraulic pressure acts and the elastic partition membrane 15 isdisplaced. Thereby a plurality of the first ribs 51 surround the latticeholes 54 every each of the rows (the inner row, outer row).

By the passage recited in claim 2 or claim 5 that “the first ribs aredisposed to be capable of surrounding lattice holes” is meant that asdescribed above, when the first ribs 51 abut on the lattice memberportions 53, the first ribs 51 surround the lattice holes 54. Because ofthat, it is not required also in the stationary state that no hydraulicpressure acts that “the lattice holes are surrounded by the first ribs”.

The second ribs 52 are disposed over the whole surface of the elasticpartition membrane 15 in a distributed manner. More particularly, asshown in FIG. 7, they are arranged in a radial fashion relative to theaxis center P of the elastic partition membrane 15.

And the second ribs 52 are set in height dimension so that tops of themmay abut on the lattice wall 18 (or the partition membranedisplacement-regulating member 17) and in a rib width smaller than thefirst ribs 51.

As illustrated in FIG. 9 on an enlarged scale, in the assembled state,the tops of the second ribs 52 on the one face of the elastic partitionmembrane 15 are made to abut on the partition membranedisplacement-regulating member 17 and the tops of the second ribs 52 onthe other face are made to abut on the lattice wall 18.

As stated above, a plurality of the first ribs 51 and a plurality of thesecond ribs 52 exist in a mutually mingled state.

This invention has been described so far on the basis of the firstembodiment, but is not limited to the first embodiment and it will bereadily appreciated that various improvements or modifications arepossible within the purview of the invention without departing from thespirit of the invention.

[1] In the first embodiment above, a plurality of the first ribs 51 areconstructed to be capable of surrounding the lattice holes 54 everyplural lattice holes, but may be constructed to be capable ofsurrounding the lattice holes 54 every one lattice hole.

That is, the rib groups 50 may comprise a plurality of the first ribs 51capable of surrounding the lattice holes 54 every one lattice hole and aplurality of the second ribs 52 disposed on either face of the elasticpartition membrane 15 in a distributed manner. Here, the pattern of thesecond ribs 52 may be other pattern than a radial pattern, as furtherstated in [4] below.

[2] In the first embodiment, it is only the first ribs 51 of the elasticpartition membrane 15 that surround a predetermined number of thelattice holes 54. However instead of that, for example, such aconfiguration is also possible that a predetermined number (one orplural) of the lattice holes 54 are surrounded each with a quadrilateralframe-shaped rib consisting of the first ribs 51 and the second ribs 52.In this case, it is also possible to set the lateral two sides of thequadrilateral frame for the first ribs 51 and the longitudinal two sidesfor the second ribs 52.

[3] This invention is also applicable to the case where the first ribs51 and the second ribs 52 do not surround the lattice holes 54.

[4] The invention is not limited to the pattern of the lattice holes 54and the patterns of the first ribs 52 and the second ribs 52 asdescribed in the first embodiment, but it is naturally possible to applyanother patterns of them to the invention.

Now the description will be given of a second embodiment of theinvention with reference to FIGS. 12 through 23. In the firstembodiment, the rib groups 50 are disposed symmetrically on both facesof the elastic partition membrane 15, whereas in the second embodiment,the first and the second displacement-regulating protrusions 151 a, 151b are disposed asymmetrically relative to a phantom plane F passingthrough the center of the elastic partition membrane 115 in thethickness direction. The parts similar to those in the first exampledescribed above are designated by like reference characters, and thedescription of them is omitted, accordingly.

FIG. 12 is a longitudinal sectional view of the hydraulic antivibrationdevice 200 in the second embodiment. The hydraulic antivibration device200 is likewise as in the first embodiment made up of the firstattachment fitting 101 to be attached to the engine side of automobiles,the second attachment fitting 102 in a cylinder form to be attached tothe vehicle body frame beneath the engine, and the vibration-isolatingbase 103 connecting the first and second attachment fittings 101, 102together and composed of a rubber-like elastomer.

The first attachment fitting 101 is formed in a columnar shape and asshown in FIG. 12, bored at its upper end face with a female portion 101a. The second attachment fitting 102 includes, as is the case with thefirst embodiment, a cylindrical fitting 104 to which thevibration-isolating base 103 is vulcanization molded, and the cup-shapedbottom fitting 105. The bottom fitting 105 is slanted at its bottompart.

The vibration-isolating base 3 is configured in a conical frustum shapeas in the first embodiment and vulcanization bonded between the firstattachment fitting 101 and the cylinder fitting 104. Thevibration-isolating base 3 is joined at its lower end to a rubbermembrane 107 covering the inner peripheral face of the cylindricalfitting 104.

The second attachment fitting 102 is, as is the case with the firstembodiment, attached with the diaphragm 9, between which and theunderside of the vibration-isolating base 103 there is formed theliquid-filled chamber 8. The liquid-filled chamber 8 is divided by thepartition 112 between the first liquid chamber 11A on thevibration-isolating base 103 side and the second liquid chamber 11B onthe diaphragm 9 side.

As for the diaphragm 9, its attachment plate 10 is fixed by crimping tothe second attachment fitting 102, and the partition 112 is pinched andheld in place between the diaphragm 9 and the step 57 of thevibration-isolating base 103.

The partition 112 is made up of the elastic partition membrane 115fashioned in a disc shape from a rubber membrane, the cylinder member116 accommodating the elastic partition membrane 115 to receive it onthe lattice wall 118 on the inner peripheral face side, and thepartition membrane displacement-regulating member 117 in a lattice discshape infixed in the opening at the lower side (lower side in FIG. 12)of the cylinder member 116.

Thus the lattice wall 118 and the partition membranedisplacement-regulating member 117 are disposed to be spaced apart apredetermined distance from each other in a mutually opposing manner,whereby the displacement amount of the elastic partition membrane 115 isregulated from both upper and lower sides, as is the case with the firstembodiment.

Between the outer peripheral face of the cylinder member 116 and therubber membrane 107 covering the inner peripheral face of the secondattachment fitting 102, the orifice 125 for bringing the first liquidchamber 11A and the second liquid chamber 11B into communication witheach other is formed so as to make one round about the axis center O ofthe cylinder member 116.

In the second embodiment, the outer periphery of the elastic partitionmembrane 115 is pinched and held between the lattice wall 118 and thepartition membrane displacement-regulating member 117 without clearance,so that communication between the first liquid chamber 11A and thesecond liquid chamber 11B through the lattice holes 154, which will bedescribed below, is completely shut out. Consequently, the liquid withinthe liquid-filled chamber 8 flows only through the orifice 125 betweenthe first liquid chamber 12A and the second liquid chamber 11B.

The following description is made of the cylinder member 116constituting the partition 112 with reference to FIGS. 13 and 14.

The cylinder member 116 is, as illustrated in FIGS. 13 and 14,configured in a cylinder shape having an axis center Q. The cylindermember 116 is provided at its axially upper and lower ends withorifice-forming walls 122 projecting in a nearly flange-like form, andbetween opposing faces of the orifice-forming walls 122 there is formedthe orifice passage R1.

The upper and lower orifice-forming walls 122 are formed with cutouts155, 158, respectively, and the orifice passage R1 communicates throughthe cutout 155 with the first liquid chamber 11A and through the cutout158 with the second liquid chamber 11B.

On the inner periphery side of the cylinder member 116, as shown inFIGS. 13 and 14, there is formed the lattice wall 118, which is piercedwith the lattice holes 154. The lattice holes 154 are of three rows oflattice holes 154A to 154C juxtaposed in the circumferential direction.

As illustrated in FIG. 13, the number of the respective lattice holes154A to 154C is six in the inner row (lattice holes 154A), eight in theintermediate row (lattice holes 154B) and four in the outer row (latticeholes 154C), and the respective lattice holes 154A to 154C are disposedequiangularly (at intervals of 60 degrees, 45 degrees, and 90 degrees inturn from the inner row) in the circumferential direction.

The configurations of the respective lattice hole rows are as shown inFIG. 13 such that the inner row is of circular lattice holes 154Aarranged in the circumferential direction, and the intermediate andouter rows are of respective radially divided annular holescircumferentially extending. The width of the lattice holes 154B is madesubstantially the same as the diameter of the lattice holes 154A andwider than that of the lattice holes 154C.

Referring to FIG. 15, the partition membrane displacement-regulatingmember 117 constituting the partition 112 will be described.

The partition membrane displacement-regulating member 117 is configured,as shown in FIGS. 15 (a) and (b), in a disc shape having an axis centerS. The partition 112 is assembled by infixing the partition membranedisplacement-regulating member 117 in the cylinder member 116 on itsinner periphery side (cf. FIG. 12). Here, the positioning of thepartition membrane displacement-regulating member 117 is conducted byengaging the upper extremity of the partition membranedisplacement-regulating member 117 with a step (cf. FIG. 14) of thecylinder member 116 formed on its inner periphery side.

The partition membrane displacement-regulating member 117 is, as shownin FIG. 15, configured to have three rows of the lattice holes 154Athrough 154C juxtaposed in the circumferential direction. The pattern ofthese lattice holes 154A˜154C (number, shape, position around the axiscenter S, etc.) is the same as that of the lattice wall 118, and thedescription of them is omitted, accordingly.

In the assembled state of the partition 112 (cf. FIG. 12), thepositional relation of the partition membrane displacement-regulatingmember 117 to the lattice wall 118 is not particularly limited. That is,the circumferential positions of the respective lattice holes 154A˜154Cof the partition membrane displacement-regulating member 117 may becircumferentially deviated to the respective lattice holes 154A˜154C ofthe lattice wall 118 or may coincide circumferentially with them.

Now the elastic partition membrane 115 will be described with referenceto FIGS. 16 and 17.

The elastic partition membrane 115 is provided, as shown in FIGS. 16 and17, with the first displacement-regulating protrusions 151 a and thefirst auxiliary protrusions 152 a projecting from its one face side andthe second displacement-regulating protrusions 151 b and the secondauxiliary protrusions 152 b projecting from the other face side.

The first and the second displacement-regulating protrusions 151 a, 151b are rib-like protrusions configured to have mutually the sameprotrusion height and protrusion width, and as shown in FIG. 16, fourpieces each of the former and the latter are provided to extend in aradial rectilinear fashion from the axis center T of the elasticpartition membrane 115 toward outwardly.

These first and second displacement-regulating protrusions 151 a, 151 bare disposed equidistantly (intervals of 90 degrees) in thecircumferential direction as depicted in FIG. 16, and the firstdisplacement-regulating protrusions 151 a on the one face side arearranged to deviate relative to the second displacement-regulatingprotrusions 151 b on the other face side by a predetermined rotationangle in the circumferential direction. Therefore the firstdisplacement-regulating protrusions 151 a are arranged in an asymmetricposition to the second displacement-regulating protrusions 151 brelative to the phantom plane F.

Here, by the phantom plane F is meant an imaginary plane that passesthrough a center in the thickness direction of the elastic partitionmembrane 115 (a membrane part provided with the respectivedisplacement-regulating and auxiliary protrusions 151 a, 151 b, 152 a,152 b) and is orthogonal to the axis line T of the elastic partitionmembrane 115.

For instance, in this second embodiment, since the first and seconddisplacement-regulating protrusions 151 a, 151 b are configured in thesame protrusion height, the phantom plane F in a cross-sectional shapeincluding the axis line T (FIG. 17) is parallel to both a plane linkingthe tops of the first displacement-regulating protrusions 151 a and aplane linking the tops of the second displacement-regulating protrusions151 b.

Here, the rotation angle at which the first displacement-regulatingprotrusions 151 a on the one face side are deviated circumferentally tothe second displacement-regulating protrusions 151 b on the other faceside is set at 45 degrees. As a consequence, the firstdisplacement-regulating protrusions 151 a (or the seconddisplacement-regulating protrusions 151 b), when viewed in the plane ofthe elastic partition membrane 115 shown in FIG. 16 (a) or (c), aredisposed each in the intermediate position between a pair of mutuallyadjacent second displacement-regulating protrusions 151 b (or thedisplacement-regulating protrusions 151 a).

Further, the protrusion heights of the first and the seconddisplacement-regulating protrusions 151 a, 151 b are constructed to besubstantially the same as the height of the outer periphery of theelastic partition membrane 115 as shown in FIG. 17. Thus in theassembled state of the partition 112 (cf. FIG. 12), the tops of thefirst and second displacement-regulating protrusions 151 a, 151 b aremade to abut on the partition membrane displacement-regulating member117 or the lattice wall 118.

On the other hand, the fist and the second auxiliary protrusions 152 a,152 b are rib-like protrusions having mutually the same protrusionheight and protrusion width, and configured, as shown in FIG. 16, by acombination of radial parts and annular parts relative to the axiscenter T of the elastic partition membrane 115.

Further, the first and the second auxiliary protrusions 152 a, 152 b areset smaller in protrusion width than the first and seconddisplacement-regulating protrusions 151 a, 151 b as shown in FIG. 16 andlower in protrusion height than the first and seconddisplacement-regulating protrusions 151 a, 151 b as shown in FIG. 17.

The following description will be given of evaluation test results ofstrange sounds referring to FIG. 18 through FIG. 20.

The evaluation test of strange sounds means a test measuring strangesounds generated when a relatively large amplitude vibration such ascranking vibration is input. The measurement of strange sounds wasconducted using the hydraulic antivibration device 200 in the secondembodiment by varying the shape of the elastic partition membrane 115.

More particularly, three kinds of the elastic partition membranes(hereinafter referred to as “Comparative Examples 1˜3”) as illustratedin FIG. 18 and three kinds of the elastic partition membranes(hereinafter referred to as “Examples 1˜3”) as illustrated in FIG. 19,namely six kinds in total of the elastic partition membranes weremeasured of strange sounds.

For a better understanding, FIGS. 18 and 19 are depicted by hatching thefirst and second displacement-regulating protrusions, with the first andsecond auxiliary protrusions being omitted.

Here, the only difference between Comparative Examples 1˜3 and Examples1˜3 consists in the configurations of the first and seconddisplacement-regulating protrusions, and all other shapes andcharacteristics (thickness dimension of the elastic partition membrane,rubber hardness, etc.) are the same.

As shown in FIGS. 18 and 19, with Comparative Examples 1˜3, thedisplacement-regulating protrusions on the one face are disposedsymmetrically relative to the phantom plane F passing through the centerof the elastic partition membrane in its thickness direction to those onthe other face whereas with Examples 1˜3, these are disposedasymmetrically. The elastic partition membrane 115 described in thesecond embodiment corresponds to Example 2.

FIG. 20 is a graphical representation showing the evaluation testresults of strange sounds on Comparative Examples 1˜3 and Examples 1˜3.The coordinate indicates acceleration value as a strange sound indexoutput from the body frame side (the second attachment fitting 102 side)when a predetermined vibration (frequency: 15 Hz, amplitude: ±1 mm) fromthe engine side (the first attachment fitting 101 side) is input. Theabscissa indicates dynamic spring value upon idling (frequency: 30 Hz,frequency: ±0.05 mm).

Here, the hydraulic antivibration device 200 is required to meet twocharacteristics: the one is a low dynamic spring when a small amplitudeis input upon idling (generally speaking, frequency: 20 Hz˜40 Hz,amplitude: ±0.05 mm˜±0.1 mm) and the other is a reduction of strangesounds when a large amplitude such as cranking vibration is input (ingeneral, frequency: 10 Hz ˜20 Hz, amplitude: ±1 mm˜±2 mm). Consequently,as a strange sounds evaluation test, it can be said that the morepreferable results are the left lower area in FIG. 20, where the strangesound index is better and the dynamic spring value upon idling becomeslower.

When comparing the measurement values in FIG. 20, with Examples 1˜3,when the restraining area of the elastic partition membrane by the firstand second displacement-regulating protrusions is widened (cf. FIGS. 18and 19), similarly to Comparative Examples 1˜3, the stiffness of theelastic partition membrane becomes higher, resulting in a better strangesound index, but the elastic partition membrane becomes difficult tomove, so that Examples 1˜3 show the tendency that the dynamic springvalue upon idling is aggravated.

However, as FIG. 20 indicates, it was corroborated that Examples 1˜3enable it to enhance more the strange sound index as compared withComparative Examples 1˜3 on condition that the dynamic spring value uponidling is equal, whereas it is possible to make the dynamic spring valueupon idling lower on condition that the strange sound index value isequal. This is ascribable to the asymmetric arrangement of thedisplacement-regulating protrusions on the one face side relative tothose on the other face side.

For example, Example 2 is of such arrangement that the first and thesecond displacement-regulating protrusions 151 a, 151 b are disposed tobe mutually deviated in the circumferential direction to those inComparative Example 1 (namely, disposed in asymmetric positions relativeto the phantom plane F passing through the center of the elasticpartition membrane 115 in the thickness direction), and when comparingExample 2 and Comparative Example 1, it can be corroborated that Example2 can achieve a reduction in strange sound index of ca. 60% whileensuring the dynamic spring value upon idling equal to ComparativeExample 1.

Referring to FIGS. 21 to 23, how the elastic partition membranes ofComparative Example 1 and Example 2 above are displaced upon inputtingof a large amplitude will be described in comparison with each other. InFIGS. 21 to 23, the illustration of the auxiliary protrusions 152 a, 152b is omitted.

The elastic partition membrane in Comparative Example 1 has, on the oneface and the other face thereof, the first and the seconddisplacement-regulating protrusions 151 a, 151 b disposed symmetrically,as shown in FIG. 22 (a). When a hydraulic pressure fluctuation istransmitted by inputting of a large amplitude through the lattice holes154 (not shown) to the elastic partition membrane, the elastic partitionmembrane is, as shown in FIG. 22 (b) or FIG. 22 (c), displaced towardthe hydraulic pressure direction (the arrow mark direction X or Y),namely from a higher hydraulic pressure side toward a smaller one side.

Here, the elastic partition membrane of Comparative Example 1 isdisplaced at its non-displacement-regulating part (the area where thedisplacement toward the hydraulic pressure direction by the first andsecond displacement-regulating protrusions 151 a, 151 b is notrestrained) and in particular, the displacement amount in the nearlyintermediate position having a smallest stiffness reaches a maximum. Asa result, as shown in FIG. 22 (b) or FIG. 22 (c), nearly intermediateposition of the non-displacement-regulating part impinges on thepartition membrane displacement-regulating member 17 or the lattice wall18 to generate strange sounds.

In contrast, with the elastic partition membrane of Example 2 as shownin FIG. 23 (a), the first displacement-regulating protrusions 151 a onthe one face are disposed asymmetrically to the seconddisplacement-regulating protrusions 151 b on the other face. Morespecifically, the first displacement-regulating protrusions 151 a (orthe second displacement-regulating protrusions 151 b) are providedprojectingly in an intermediate position between the seconddisplacement-regulating protrusions 151 b (or the firstdisplacement-regulating protrusions 151 a), namely on the opposite faceside in the area where the displacement amount of the elastic partitionmembrane becomes a maximum and most susceptible to contact with thelattice member.

Therefore, even though the elastic partition membrane of Example 2 isdisplaced in the hydraulic pressure direction (the arrow direction X orY) by inputting of a large amplitude, as shown in FIG. 23 (b) or FIG. 23(c), the stiffness of the intermediate position area of thenon-displacement-regulating part, namely the area where a contributionpercentage to generation of strange sounds is largest is reinforcedconvergently by the first or the second displacement-regulatingprotrusions 151 a, 151 b, so that the intermediate position area of thenon-displacement-regulating part is made difficult to displace whilesuppressing a rise in stiffness of the overall elastic partitionmembrane thereby effectively reducing strange sounds upon inputting of alarge amplitude.

As a result, according to the elastic partition membrane of Example 2,only the stiffness of the portions necessitated for reduction of strangesounds is intensified convergently thereby to retain a low dynamicspring characteristic upon inputting of a small amplitude, yet theelastic partition membrane is made difficult to contact with the latticemembers thereby to reduce effectively strange sounds upon inputting of alarge amplitude. Thus it is possible to meet the two mutually contraryrequirements to a high degree.

So far, the description has been made of the invention on the basis ofthe second embodiment, but is not construed as limiting the invention toit, and it will be appreciated that various improvements andmodifications may be made within the purview of the invention withoutdeparting from the spirit of the invention.

In the second embodiment above, the example where four pieces of thefirst displacement-regulating protrusions 151 a are configured from theaxis center T toward outwardly in a radial rectilinear fashion has beendescribed, but this number is not limitative at all. For example, it isnaturally possible to choose the number of three pieces or less or fivepieces or more. This is also true with the number of the seconddisplacement-regulating protrusions 151 b.

Again in the second embodiment above, the example where the first andthe second displacement-regulating protrusions 151 a, 151 b are disposedin a radial fashion relative to the axis center T of the elasticpartition membrane 115 has been described, but the invention is notnecessarily limited to this pattern, and another pattern is naturallyapplicable.

As another pattern, for example, a pattern of annular arrangementrelative to the axis center T a pattern of a combination of radialarrangement and annular arrangement, etc. are exemplified. By the term“radial” is not always meant rectilinear, but it includes the meaning ofa swirling curve. On the other hand, the meaning of the term “annular”is not always a complete circle, but includes also ellipsoidal,polygonal, etc.

In the second embodiment above, the example where the first and thesecond displacement-regulating protrusions 151 a, 151 b are provided soas to project from the elastic partition membrane 11 has been described,but it is not always necessary to project these bothdisplacement-regulating protrusions 151 a, 151 b from the elasticpartition membrane 115. If only at least the one of thedisplacement-regulating protrusions 151 a or 151 b are provided on theone face of the elastic partition membrane 115 and bothdisplacement-regulating protrusions 151 a, 151 b are disposed mutuallyasymmetrically, it is naturally possible to construct so that the otherof the displacement-regulating protrusions 151 b or 151 a are providedso as to project from the partition membrane displacement-regulatingmember 117 or the lattice wall 118.

Further in the second embodiment above, the example where the elasticpartition membrane 115 is provided with the first and the secondauxiliary protrusions 152 a, 152 b in a projecting manner has beendescribed, but it is not always necessary to provide these projectinglyand it is naturally possible to omit the projective provision of the oneor both of these first and second auxiliary protrusions 152 a, 152 b.

Where the projective provision of the first and second auxiliaryprotrusions 152 a, 152 b is omitted, embossing processing may be appliedto the surface of the non-displacement-regulating part (the area wherethe first and second displacement-regulating protrusions 151 a, 151 bare not provided) of the elastic partition membrane 115. It is naturallypossible also to apply embossing processing to the surface of the firstand second auxiliary protrusions 152 a, 152 b. Thereby it is possible tomake the elastic partition membrane 115 to impinge moderately on thepartition membrane displacement-regulating member 117 or the latticewall 118 to achieve the reduction of strange sounds.

In the second embodiment above, the first and seconddisplacement-regulating protrusions 151 a, 151 b in the assembled stateof the partition 112 are set in a protrusion height so that the tops ofthem may abut on the partition membrane's displacement-regulating member117 or the lattice wall 118, but are not necessarily limited to thatheight, and the protrusion height may be set so that a clearance isformed between the tops and the partition membranedisplacement-regulating member 117 or the lattice wall 118. Suchclearance is preferred to be ca. 0.3 mm or less in the assembled stateof the partition 112.

Again in the foregoing second embodiment, the example where the elasticpartition membrane 115 is employed for the hydraulic antivibrationdevice 200 of a so called single orifice type, wherein the first liquidchamber 11A and the second liquid chambers 11B are put in communicationwith each other through one piece of the orifice 125, has beendescribed, but this invention is not necessarily limited to this type,and naturally applicable to a double-orifice type of hydraulicantivibration device.

By the term “double-orifice type hydraulic antivibration device” ismeant the one comprised of a main liquid chamber, a first and a secondsubsidiary liquid chambers, and a first and a second orificescommunicating with the first and the second subsidiary liquid chambersand the main liquid chamber respectively.

INDUSTRIAL APPLICABILITY

According to the hydraulic antivibration device of the first invention,it is possible to bring a plurality of the first ribs into the statethat the tops thereof are spaced apart from the lattice members and tobring a plurality of the second ribs on either face of the elasticpartition membrane into the state that tops of them abut on the latticemembers. Thereby when the elastic partition membrane advances toward thelattice member side, attended on vibration, the second ribs resist toallow the tops of the first ribs to impinge slowly on the faces of thelattice members, and consequently, the effect accrues that strangesounds can be sufficiently reduced.

Further since the first ribs and the second ribs exist in a mutuallymingled fashion and the second ribs are made smaller in width than thefirst ribs to weaken the stiffness, the effect accrues that it ispossible to obviate the elastic partition membrane from being difficultto reciprocate.

In accordance with the hydraulic antivibration device of the secondinvention, the additional effect to the effects achieved by thehydraulic antivibration device of the first invention accrues thatbecause the second ribs are disposed on the faces of the elasticpartition membrane in a distributed manner, it is possible to prevent aresistance force of a plurality of the second ribs from concentrating ona part of the elastic partition membrane. And besides because the firstribs are disposed on the faces of the elastic partition membrane so asto be capable of surrounding the lattice holes every a predeterminednumber of them, under a large amplitude vibration condition where thetops of the first ribs abut on the lattice member, the first ribssurround the lattice holes every the predetermined number of themthereby obviating the flowing of fluid between the predetermined numberof the lattice holes and other lattice holes. Thus a further effectaccrues in that it is possible to enhance more the vibration-proofperformance.

According to the hydraulic antivibration device of the third invention,in addition to the effects achieved by the hydraulic antivibrationdevice of the second invention, a further effect accrues in that becauseunder a large amplitude vibration condition where the tops of the firstribs abut on the lattice member, a plurality of the first ribs cansurround the lattice holes every one lattice hole row and can preventthe liquid from fluidizing between the lattice holes of a certainlattice hole row and the lattice holes of adjacent lattice hole row toit, it is possible to enhance more the antivibration performance.

Again since the second ribs are disposed in a radial fashion relative tothe axis center of the elastic partition membrane, a further effectaccrues in that it is possible to preclude that the resistance force ofa plurality of the second ribs concentrates on a part of the elasticpartition membrane.

According to the hydraulic antivibration device of the fourth invention,in addition to the effects achieved by the one of the first invention,the effect accrues: because the first ribs and the second ribs arearranged on the faces of the elastic partition membrane so as to becapable of surrounding the lattice holes every a predetermined number ofthem, under a large amplitude vibration condition where the tops of thefirst ribs abut on the lattice member, the first ribs and the secondribs surround the lattice holes every the predetermined number of them,and consequently, it is possible to prevent the fluid from flowingbetween the predetermined number of the lattice holes and other latticeholes, thus enhancing more the antivibration performance.

According to the hydraulic antivibration device of the fifth invention,because the ribs play the role of a cushion when the elastic partitionmembrane impinges on the lattice members, attended with vibration, it ispossible to bring the elastic partition membrane into moderateimpingement on the lattice members, which results in the effect thatstrange sounds can be reduced.

And under a large amplitude vibration condition where the tops of theribs abut on the lattice members, the ribs surround the lattice holesevery a predetermined number of them, and consequently, it is possibleto avoid the fluidization of fluid between the predetermined number ofthe lattice holes and the other lattice holes, thus preventing areduction in antivibration performance.

Further because the one lattice member of a pair of the lattice membersis provided to link integrally with the cylinder member between innerperipheral faces thereof, it is possible to set the posture of thelattice member to the cylinder member (for example, the perpendicularityof the cylinder member to the axis center) accurately as compared withthe construction such that either of the lattice members is configuredof a separate member from the cylinder member. Moreover it is possibleto set accurately the distance between both lattice members when theother lattice member is attached to the cylinder member, and to setaccurately the clearance between the elastic partition membrane and theboth lattice members, accordingly. Therefore the effect accrues that itis thereby possible to more enhance the antivibration performance.

According to the hydraulic antivibration device of the sixth invention,it is possible to bring about the states that the tops of a plurality ofthe ribs are spaced apart from the lattice members and the tops of aplurality of the auxiliary ribs on either face of the elastic partitionmembrane abut on the lattice members. Thereby when the elastic partitionmembrane advances toward the lattice members with vibration, theauxiliary ribs resist thereby to allow the tops of the ribs to impingemoderately on the lattice members, and consequently, the effect accruesthat strange sounds can be sufficiently reduced.

Further effect accrues in that because the auxiliary ribs are disposedon the faces of the elastic partition membrane in a distributed manner,it is possible to preclude that the resistance force of a plurality ofthe auxiliary ribs concentrates on a part of the elastic partitionmembrane and concurrently because the auxiliary ribs are made smaller inwidth than the ribs, thus being made weak in stiffness, it is possibleto preclude that the elastic partition membrane becomes difficult toreciprocate.

And under a large amplitude vibration condition where the tops of theribs abut on the lattice members, the ribs surround the lattice holesevery a predetermined number of them, and hence, it is possible topreclude that the fluid fluidizes between the predetermined number ofthe lattice holes and other lattice holes than these, which results inthe effect that it is possible to more enhance the antivibrationperformance.

According to the hydraulic antivibration device of the seventhinvention, in addition to the effects achieved by the hydraulicantivibration device of the sixth invention, the following effectaccrues: because under a large amplitude vibration condition where thetops of the ribs abut on the lattice members, a plurality of the ribssurround the lattice holes every one lattice hole row, and hence, it ispossible to preclude that the liquid fluidizes between the lattice holesof an arbitrary lattice hole row and the lattice holes of an adjacentlattice hole row thereto and ultimately it is possible to prevent areduction in antivibration performance.

Again since the auxiliary ribs are disposed in a radial fashion relativeto the axis center of the elastic partition membrane, further effectaccrues that it is possible to avoid concentration of the resistanceforce of the plural auxiliary ribs on a part of the elastic partitionmembrane.

According to the hydraulic antivibration device of the eighth invention,the device has the first displacement-regulating protrusions providedprojectingly on the one face side of the elastic partition membrane andthe second displacement-regulating protrusions provided projectingly onthe other face side of the elastic partition membrane or the latticemember facing the other face side. Thus when the elastic partitionmembrane is displaced toward the lattice member, attended with the largeamplitude vibration, the displacement of the elastic partition membranecan be regulated by the first or the second displacement-regulatingprotrusions disposed on the displacement direction side, so that theeffect accrues that it is possible to suppress the impingement betweenthe elastic partition membrane and the lattice member to reduce strangesounds.

Further the elastic partition membrane is, at least on its one faceside, provided with the first displacement-regulating protrusions in anasymmetric position to the second displacement-regulating protrusions.Because of that, when the elastic partition membrane is displaced towardthe lattice member on the second displacement-regulating protrusionsside, attended with the large amplitude vibration, the firstdisplacement-regulating protrusions provided projectingly on theopposite side to the displacement direction can reinforce locally thestiffness of the elastic partition membrane thereby making thedisplacement of the elastic partition membrane difficult. Consequentlythere accrues the effect that by that amount, it is possible to suppressthe contact of the elastic partition membrane with the lattice member toachieve a further reduction of strange sounds.

On the other hand, the first and the second displacement-regulatingprotrusions are disposed in a mutually asymmetric position relation,whereby it is possible to make the influence that the onedisplacement-regulating protrusions give on the stiffness of thenon-displacement regulating part on the other displacement-regulatingprotrusions side smaller, and hence, the effect accrues that whilesuppressing the stiffness of the entire elastic partition membrane to alow degree, it is possible to suppress effectively the contact of theelastic partition membrane with the lattice members. Stated another way,it is possible to reduce strange sounds upon inputting of a largeamplitude, while maintaining a low dynamic spring characteristic uponinputting of a small amplitude.

Here, the contribution degree to generation of strange sounds differsgreatly depending upon whether the party with which the elasticpartition membrane contacts is the lattice member on the first liquidchamber side or the lattice member on the second liquid chamber side.According to the construction described above wherein the first and thesecond displacement-regulating protrusions are displaced in mutuallyasymmetric positions, it is possible to adjust appropriately thestiffness ratio of the one face side to the other face side of theelastic partition membrane. Hence, while elevating the stiffness of theone face side thereby to make it difficult for the elastic partitionmembrane to contact with the lattice member whose contribution degree togeneration of strange sounds is larger, the stiffness of the other faceside is made lower, whereby it is possible to suppress a rise instiffness of the entirety of the elastic partition membrane. As aconsequence, there is the effect that mutually contrary requirements ofa reduction of strange sounds upon inputting of a large amplitude andthe maintaining of a low dynamic spring characteristic upon inputting ofa small amplitude can be satisfied.

According to the hydraulic antivibration device of the ninth invention,in addition to the effects achieved by the one of the eighth invention,the further effect accrues: because the second displacement-regulatingprotrusions are provided projectingly from the other face side of theelastic partition membrane, a complex working to the lattice members isdispensed with and the production cost attended on the formation of thesecond displacement-regulating protrusions can be reduced, and by thatamount, a reduction of product cost as an overall hydraulicantivibration device can be achieved.

According to the hydraulic antivibration device of the tenth invention,in addition to the effects achieved by the hydraulic antivibrationdevice of the eighth or ninth invention, the effect accrues: because atleast part of the first and the second displacement-regulatingprotrusions is disposed in a radial fashion relative to the axis centerof the elastic partition membrane, it is possible to make it difficultfor the elastic partition membrane to contact with the lattice memberthereby to reduce strange sounds upon inputting of a large amplitude,while suppressing a rise in stiffness of the elastic partition membraneas a whole thereby to maintain a low dynamic spring characteristic uponinputting of a small amplitude.

Further at least a part of the first displacement-regulating protrusionsare provided in an intermediate position between the seconddisplacement-regulating protrusions, namely in the area where theelastic partition membrane reaches a largest displacement amount and ismost susceptible to contact with the lattice member. Therefore it ispossible to reinforce convergently the stiffness only of the area wherethe contribution degree to generation of strange sounds is largest bythe first displacement-regulating protrusions, and hence, it is possibleto reduce effectively strange sounds upon inputting of a large amplitudewhile suppressing a rise in stiffness of the entirety of the elasticpartition membrane. As a result, the effect accrues that it is possibleto meet highly the mutually contrary requirements of: a reduction ofstrange sounds upon inputting of a large amplitude by making the contactof the elastic partition membrane with the lattice member difficultwhile maintaining a low dynamic spring characteristic upon inputting ofa small amplitude.

According to the hydraulic antivibration device of the eleventhinvention, in addition to the effects achieved by the one of the ninthinvention, the following effect accrues: because the first and thesecond displacement-regulating protrusions respectively in n pieces, aredisposed in a radial fashion and equidistantly in the circumferentialdirection, and the first displacement-regulating protrusions aredeviated circumferentially by a rotation angle of ca. π/n to the seconddisplacement-regulating protrusions, namely, each the firstdisplacement-regulating protrusion is disposed in the intermediateposition between mutually adjacent second displacement-regulatingprotrusions, it is possible to reinforce convergently the stiffness onlyof the area whose contribution rate to generation of strange sounds islarge, while suppressing a rise in stiffness of the elastic partitionmembrane as a whole. As a consequence, it is possible to meet, to a highdegree, mutually contrary requirements that strange sounds should bereduced upon inputting of a large vibration amplitude while maintaininga low dynamic spring characteristic upon inputting of a small vibrationamplitude.

Further because the first and the second displacement-regulatingprotrusions are configured in mutually substantially the same protrusionheight and the same protrusion width, it is possible to render thestiffness of the elastic partition membrane on its both facesapproximately the same. Therefore in the assembling process of thehydraulic antivibration device, in incorporating the elastic partitionmembrane between the lattice members of the partition, there is nonecessity of identifying the elastic partition membrane as to thereverse face or the front face thereof, and hence further effect accruesin that the incorporating work is simplified and by that amount, areduction in working cost can be achieved.

Further effect in the assembling process is that even though any workingperson errs in the incorporating direction of the reverse and frontfaces of the elastic partition membrane, it is possible to suppress andminimize the influence affecting on strange sounds because stiffness ofthe elastic partition membrane is the same on the reverse and frontfaces.

According to the hydraulic antivibration device of the twelfthinvention, in addition to the effects achieved by the hydraulicantivibration device of any one of the eighth invention to the eleventhinventions, the following effect accrues: because the first and thesecond displacement-regulating protrusions are configured in a heightthat the tops of them can abut on the lattice member or the elasticpartition membrane, namely, in the state that there is no clearancebetween the respective displacement-regulating protrusions and theelastic partition membrane or the lattice member, when the elasticpartition membrane is displaced toward the lattice members, attendedwith vibration, it is possible to avoid the contact of the respectivedisplacement-regulating protrusions with the elastic partition membraneor the lattice member that causes to generate strange sounds.

According to the hydraulic antivibration device of the thirteenthinvention, in addition to the effects achieved by the hydraulicantivibration device of any one of the eighth invention to the twelfthinvention, the effect accrues that because the elastic partitionmembrane is provided on the one face side and the other face sidethereof with the auxiliary protrusions, even though the elasticpartition membrane contacts with the lattice members, it is possible tobring the tops of the auxiliary protrusions into contact with thelattice members, thereby rendering the contact area with the latticemembers small and simultaneously making a moderate contact of theelastic partition membrane with the lattice members by the cushioningaction of the auxiliary protrusions, so that it is possible to achieve areduction of strange sounds by that amount.

A further effect accrues in that because the auxiliary protrusions areconstructed lower in protrusion height and narrower in protrusion widththan at least the first displacement-regulating protrusions, it ispossible to suppress that the stiffness of the elastic partitionmembrane as a whole is raised, to maintain a low dynamic springcharacteristic upon inputting of a small amplitude.

According to the elastic partition membrane of the fourteenth invention,it is possible to achieve a similar effect to that of the elasticpartition membrane used for the hydraulic antivibration device of anyone of the first to the thirteenth inventions.

1. A hydraulic antivibration device comprising: a first attachmentfitting, a cylindrical second attachment fitting, a vibration-isolatingbase connecting the second attachment fitting and the first attachmentfitting to each other and composed of an elastomer, a diaphragm attachedto the second attachment fitting to form a liquid-filled chamber betweenthe diaphragm and the vibration-isolating base, a partition compartingthe liquid-filled chamber into a first liquid chamber on thevibration-isolating base side and a second liquid chamber on thediaphragm side, and an orifice putting the first liquid chamber and thesecond liquid chamber into communication with each other, the partitionincluding an elastic partition membrane and a pair of lattice membersregulating the displacement amount of the elastic partition membranefrom both sides thereof, wherein rib groups are provided projectingly onboth faces of the elastic partition membrane, and include a plurality offirst ribs and a plurality of second ribs, said first ribs intersectingwith said second ribs, wherein the first ribs are set in heightdimension so that tops thereof may be situated to be spaced apart fromthe lattice members; and wherein the second ribs are set in heightdimension so that tops thereof may abut on the lattice members and in arib width smaller than the first ribs.
 2. The hydraulic antivibrationdevice as set forth in claim 1, wherein the first ribs are disposed onthe faces of the elastic partition membrane so as to surround apredetermined number of lattice holes; and wherein the second ribs aredisposed on the faces of the elastic partition membrane in a distributedmanner.
 3. The hydraulic antivibration device as set forth in claim 2,wherein the lattice holes are disposed in a plurality of rows in thecircumferential direction of the lattice members; wherein said pluralityof the first ribs are formed in an annular form and abut on respectivelattice member portions on radially both sides of respective latticehole rows of the lattice members; and wherein said plurality of thesecond ribs are disposed in a radial fashion relative to an axis centerof the elastic partition membrane.
 4. The hydraulic antivibration deviceas set forth in claim 1, wherein the first ribs and the second ribs aredisposed on the faces of the elastic partition membrane so as tosurround a predetermined number of lattice holes.
 5. A hydraulicantivibration device comprising: a first attachment fitting, acylindrical second attachment fitting, a vibration-isolating baseconnecting the second attachment fitting and the first attachmentfitting to each other and composed of an elastomer, a diaphragm attachedto the second attachment fitting to form a liquid-filled chamber betweenthe diaphragm and the vibration-isolating base, a partition compartingthe liquid-filled chamber into a first liquid chamber on thevibration-isolating base side and a second liquid chamber on thediaphragm side, and an orifice putting the first liquid chamber and thesecond liquid chamber into communication with each other, the partitionincluding an elastic partition membrane, a cylinder portionaccommodating the elastic partition membrane, and a pair of latticemembers regulating the displacement amount of the elastic partitionmembrane within the cylinder portion from both sides thereof, whereinone lattice member of the pair of the lattice members is provided tolink integrally with the cylinder portion between inner peripheral facesof the cylinder portion; wherein the elastic partition membrane isprovided on both faces thereof with a plurality of first ribssurrounding a predetermined number of lattice holes and with a pluralityof auxiliary ribs disposed in a distributed manner; wherein said firstribs are set in height dimension so that tops of thereof may be situatedto be spaced apart from the lattice members; wherein said auxiliary ribsare set in height dimension so that tops thereof may abut on the latticemembers and in a rib width smaller than the ribs, wherein the latticeholes are disposed in a plurality rows in the circumferential directionof the lattice members; wherein said plurality of first ribs areconfigured in an annular form so that they may abut on portions of thelattice members on radially both sides of the respective lattice holerows of the lattice members; and wherein said auxiliary ribs radiallyextend relative to the axis center of the elastic partition membrane.